New to Elevation Certificates - Questions

Height transfer via GPS can be tricky. First and foremost, the geoid in your area of interest must be well-modeled. If the geoid model is good, then you have options.

Given the liability involved, I'd want to be able to point to authoritative procedures to back up my work, and that means NGS height modernization guidelines, unless LSU has published an alternate procedure. It's possible that your VRS provider has a reliable height transfer procedure available.

There are a lot of variables as to implementation: how many receivers do you have available, do your local CORS have valid orthometric heights, do you have reliable local bench marks that you can occupy? More questions than answers, I'm afraid.

I hope you have your flame proof underwear on. I will try to give some constructive criticism.
First, you can't be worrying about the going rate and the hourly time. You need to worry about getting the data correct. The problem with GPS and OPUS is that you can set the unit in an open area and collect for 2 hours and still have a problem with the data. Bad satellite geometry, garbage info from a CORS site, etc. To be honest, my first thought is to find the reference marks for the current (or past maps) and measure from them using conventional leveling.
Getting a good elevation is the first stage. Second stage is getting all the data needed correctly. Third is filling out the form.
Can you identify a foundation vent vs a flood vent? Can your guys? How is a subsurface crawlspace defined?
You have to know some surveyors in the area, why not partner and send your guys with them to piggyback and learn.
Around here (southeast, Virginia) we are no stranger to the flood program, and we still have FEMA seminars packed with surveyors asking questions about the Certificate and situations that don't fit the Cert.

Many situations don't fit the cert. You have to use the best fit and explain in the notes.

Basement vs crawlspace is a big danger zone. Throw away the pre conceived notion of the difference. Someone may have a crawlspace and call it so, you may look at it and say 'wow ya that's a crawlspace alright!' But it may actually fit the criteria and be a full basement via the certificate instructions.

I'm not sure how our geoid is in my area, but I've checked my GPS via known ngs disks and hit within a tenth each time I check.

And as fema will tell you, always err on the side of caution.

What does the flood map in that area use for elevations? Should you use the bench marks on the map (which have probably subsided), or best determination of true orthometric height, the more pessimistic of the two, or what?

Bill93, post: 389556, member: 87 wrote: Should you use the bench marks on the map (which have probably subsided), or best determination of true orthometric height

If FEMA recognizes the site as in a subsiding area, you can't rely on the published mark elevations. The folks around New Orleans know a lot more about this than I do, and can detail the history -- including costly surveyor liability -- of what happens if you use subsided marks.

If the area isn't recognized by FEMA as subsiding, it's a harder call. If the surveyor has knowledge that a mark has subsided significantly and still uses the published value, I think he sets himself up for trouble. All the recent (last 10 years or so) FEMA updates in my area omit reference mark elevations and refer instead to the NGS IDB, which should work okay for stable areas.

FEMA does allow an OPUS solution as the elevation reference. You have to attach the OPUS report to the Elevation Certificate.

Andrew, since we are located in the Florida Parishes of our state, I will make the following comments.
First of all, setting a TBM for construction is not part of producing an EC. An EC can be completed by an PE, architect and/or PLS.

Setting a TBM or CBM is usually done as a separate task as part of what's known as a "Builder's Package" by a PLS. But a client (homeowner or contractor) can request that only a TBM be set. BUT most Parish/City building permit departments and loan/grant providers want a stamped survey for construction providing boundary showing property lines, setbacks and easements and utility access. This is the venue of a PLS. All construction plans that I have seen have had the site TBM set by a PLS. Maybe there has been updated policies...

Secondly, ECs are high liability.(ask any surveyor in LA) If a building is being constructed at the wrong BFE and the foundation is built...you just bought something really expensive you didn't want to buy. That being said, having a solo field tech as being in responsible charge for establishing elevations without oversight can be a risk. It only takes one screwup.
There is a successful surveyor that I know here who I have not always agreed with his surveys or business practices. Once, we were having a private discussion about ECs and establishing elevations and he told me that setting elevations caused him nightmares. He explained how he could "see or sense" boundaries in the field and recover evidence but for elevations this was not possible. We discussed sound procedures and QC as the only way to alleviate fears of the unknown Z.

I have done many ECs solo.
Scheduling is important and communication with the owner for access.
Basic procedure was to set a rod/cap subsurface in a good GPS view... Collect for a few hours static with dual frequency unit. (If there was a reliable NGS mark in the vicinity, I would place another receiver to observe)
While receivers were cooking, using an optical level, Rods with bipods/tripods and field book, record all the data required for the EC (FFE,adjacent ground, NG,HVAC pads,enclosed garage floor, etc.) tape for square footage,
Take all pictures and whatever else.
If a TBM was requested,set a nail somewhere near, transfer ?elevation from control point to nail. Take pictures and document. There are little tricks and methods one picks up along the way.

Wrap to the office. Download receivers, process data with GNSS software.also download CORS to process. See what it smells like and then OPUS submissions.
I was also fortunate to have established a vertical network here using NGS procedures and also having access to a colleague network for QC.
Consult with local
FPA and get documentation of the BFE determination.
Annotate photos using Adobe Elements.
Fill out Form
Insert photos
Stamp/sign
(May have left something out, multitasking here and posting from phone)

For the TBM, prepare a separate letter (signed/stamped)stating the elevation information for the TBM and it's relation to the local FPA's documented BFE.
Attached separate sheet with annotated photo of TBM with full description.
(Type,location, position,relation to NG and 2 point tie)
Attach Invoice

Feel free to contact me with any questions

geaux tigers

Baton Rouge isn't subject to nearly the subsidence rates as in the New Orleans area. The going rate for elev certs around here ranges from $225 to $350. At that price there is no way anyone is leveling from an existing benchmark unless it happens to be adjacent to the property. Everyone uses GPS, most likely the LSU RTN, which is allowable by FEMA. I would rather do a static session than use VRS alone. I could take VRS shots at the beginning and end as well as collect static while we're leveling. Average the VRS shots as additional QA/QC for the static as well as give me a number to use to set an approximate BFE mark for the building owner. Use the static for the cert, assuming it checks out with the VRS.

I have spoken with a PLS in the area, actually a fellow board member, but would like to solicit other opinions.

This type of low-cost, high-volume work is new to me. But I want to ensure that every one I stamp is as correct as it can be, based on standard industry practice.

Thanks for your help.

Thanks Robert. I'll give you a call next week to meet up and discuss.

andrewm, post: 389568, member: 10888 wrote: The going rate for elev certs around here ranges from $225 to $350.

Wow. I just finished one this morning, it was a little more involved than usual because of the BFE source, but I charged $1,830.00.

Exactly. But, if we're super efficient, we can make it work for that price. Certainly won't make much profit, but I'll keep my field guys busy and possibly meet someone that has a bigger project need.

Lots of great advice above.

Lock in on only the best benchmarks. Forget GPS for elevation, go old school. The risk is too great. Do not attempt to set some standard price. Charge for everything you must do. Don't worry about the competition. Making a profit at minimal risk is far more important.

Like I said from the start, I'm new at this. However, if you just look at the EC alone without setting a BFE Mark on the property, clearly FEMA allows engineers and architects to do these in addition to surveyors. By that alone it seems that FEMA doesn't consider the EC to be a rigorous professional surveying document. They let architects do it for heavens sake! (No offense to any architects around here!) The primary purpose of an EC is purely for insurance rates correct? So what is the real risk here strictly relating to elevations collected in the field for the EC? Determining premium correct? The higher you are relative to the BFE, ther lower your rate. So, if I perform the EC as outlined by FEMA guidelines and their accepted methodology, FEMA should accept it, right? So strictly to that point, the risk to me seems minimal.

Now I realize the EC will also be used to get a building permit to rebuild. If a building in the 100-yr flood zone received substantial damage (>50% of its market value) and is below BFE, a permit will not be issued to rebuild until the structure is raised. So let's look at my risk here. If the building is clearly above or below the BFE (say greater than 1'), then I feel really good about using the GPS procedures outlined above to perform the EC and wouldn't think twice about it. If once I do the EC and see that the building is really close to the BFE, perhaps then I should look at a much longer static session (>4 hours) or level from a benchmark to be sure.

I do agree that setting a TBM at the BFE is really outside the scope of the EC and should be performed at a later time using a different technique.

Thoughts??

FEMA may allow architects and engineers to fill out certificates but does your state? I'd turn any architect or engineer into their board for doing them here.

Engineers for sure can do them here. In fact only boundary surveying is restricted to surveyors. Engineers can do any other type of surveying and mapping.

Yes, this is a State by State final decision. alphasurv may want to double check the specific ruling on this for his State.

Holy Cow, post: 389578, member: 50 wrote: Lots of great advice above.

Lock in on only the best benchmarks. Forget GPS for elevation, go old school. The risk is too great. Do not attempt to set some standard price. Charge for everything you must do. Don't worry about the competition. Making a profit at minimal risk is far more important.

Impossible to level from Classic NGS BMs for the past 10 years. Even
NGS gave up on doing so
And ADVISED others to
Do the same.
It's why CORS was expedited in Louisiana. Then the implementation of Gulfnet.
Post Katrina after the great NGS BM purge, we established various Vertical
Control networks using NGS protocols and that was going to be as good as it gets. One network here was established using the local
HARN station at an airport. Days of sitting on that station to develop control
Network with long static sessions.
After analysis by every which way and the other, we found a 3 cm
Difference from the published.
Not bad. When we QCed into another network previously established, that difference was half the 3cm.
A year or so later, I got a call from a survey tech of a company not from this area. They were virgin users of the LSU RTN. I suspected a lot of button pushing going on. He told me that they had checked into a TBM that I set and had a large disagreement. I requested their data and said that I would send mine along upon delivery of their data.
Never heard back from them or anyone else. Never even found out what TBM
They tied to...since there were a few in
that area.

I received a similar call within the past year in our stable environment. The guy was getting a number something like three feet different from the long established benchmarks the whole city was built from. Never found out where he went wrong but highly recommended he stick with what every other surveyor and DOT had been using for years, adjusted about 0.42' for the change from old to new. New datum values are about that much greater than the old datum. Otherwise he was going to have a lot of fun matching the highway and the sewer system.

I always just thought the certificate had a check box for "architect" for ECs done based off of building plans for proposed structures. NOT completed structures.

I wouldn't see any reason for an architect to do an EC based on field data collection. Or an engineer. So I would definitely check.

The form states "This certification is to be signed and sealed by a land surveyor, engineer, or architect authorized by law to certify elevation information."

In Louisiana engineers can absolutely certify elevation information. From the La engineering and surveying law:

"c. Surveying and mapping functions which do not require the establishment of the relationship of property ownership boundaries must be performed by or under the responsible charge of either a professional engineer or a professional land surveyor. Such surveying and mapping functions include:

i.surveys of servitudes (easements) and rights of way;
ii.surveys of leases;
iii.topographical surveys;
iv.surveys for record drawing;
v.layout surveys for construction;
vi.hydrographic surveys;
vii.mine surveys;
viii.mapping;
ix.geodetic surveys;
x.cartographic surveys;
xi.horizontal and vertical control surveys;
xii.quantity and measurement surveys;
xiii.profiles and cross-sections;
xiv.site grading plans."